Aurelia Turbines develops and manufactures small gas turbines that can run on various fuels.
Both gas turbines and reciprocating engines are internal combustion engines, in which the energy from the combustion of fuel is converted into mechanical motion. However, gas turbines, used in industry and power generation, and reciprocating engines, used in cars, are structurally different.
What is a gas turbine?
- A gas turbine is a thermal engine. Gas or liquid fuel is burned in a combustion chamber, and a shaft connects the turbine to a supercharger that compresses air into the combustion chamber.
- Gas turbines are based on continuous combustion, in which expanding combustion gases rotate the shaft as they exit the combustion chamber through a turbine impeller (axial turbines) or a turbine wheel (radial turbines). The rotating shaft pressurises the air in the combustion chamber for combustion, and, for example, electricity can be generated in the generator.
- Gas-turbine–generator combinations generate a significant portion of the world's electricity.
- Aircraft jet turbines are also gas turbines by their internal structure, although they have other differences compared to turbines in power plants, for example.
What are reciprocating engines?
- In a reciprocating engine, often referred to as a piston engine, the mixture of fuel and air ignites from either hard compression (diesel engine) or a spark plug (petrol and gas engines). The expanding combustion gas pushes the piston, and eventually, the piston returns to its initial position. The reciprocating motion of the piston is converted into a usable rotary motion by means of a crank and a crankshaft. This rotary motion can be converted, for example, in a generator to generate electricity locally.
- Reciprocating engines are for power generation. For example, cars running on gasoline and diesel have reciprocating engines.
- Reciprocating engines have been around for decades, and the technology is well-established. Reducing emissions and improving the efficiency of reciprocating engines from this point are challenges.
- The reciprocating engine is a relatively strong solution for sole power generation in small- and medium-sized power plants. In contrast, the reciprocating engine is clearly weaker in combined heat and power generation, especially in terms of industrial needs.
- In a reciprocating engine, combustion takes place in fast, separate cycles, each of which must be ignited each time: a six-cylinder engine generator running at 1,500 rpm has 4,500 separate combustion events per minute.
- Exhaust emissions from reciprocating engines can be high. Emissions include nitrogen oxides (NOx) and carbon monoxide (CO).
- Only a few fuels are suitable for reciprocating engines because the combustion event is limited as described above. Typically, reciprocating engines can use standard fuels, such as gasoline and diesel. If fuels do not meet the combustion requirements of the engine, the engine may run poorly or stop altogether, possibly causing damage.
- Reciprocating engines are oil-lubricated and have several moving components. As a result, they require more frequent maintenance than gas turbines.
Why turbines instead of engines?
- Turbines can be designed to be efficient for both electricity and heat production.
- In a turbine, the combustion process starts when the turbine starts. Once combustion is achieved, the temperature remains stable at all stages of the process. As a result, fuel combustion is cleaner, producing significantly lower emissions than a reciprocating engine.
- In principle, a gas turbine is not particularly demanding in terms of fuel choices. The design of the gas turbine allows a broader range of fuels than a reciprocating engine.
- Lubricants and, therefore, lubricant-cooling are not required in the turbine when using active magnetic bearings. In this case, the leakage of lubricant into the exhaust gases and the resulting small particles and problematic compounds produced by oil coagulation are eliminated from the flue gasses.
- Active magnetic bearings increase the longevity of other parts and reduce emissions.
- Turbine technology can be further improved through the development of new materials, high-speed technology and frequency converters.